Pump



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Z ZiQa/vle A r TORNE rs Patented July 27, 1954 UNITED STATES ATENT OFFICE PUMP poration Application January 29, 1951, Serial No. 208,381

This invention relates to new and useful improvements in pumps.

One object of the invention is to provide an improved pump which is particularly adapted for use in pumping fluid from well bores and which is constructed to displace or lift an increased volume of fluid from the well with a given stroke length operating at a given number of strokes per minute.

In the usual single stroke well pump, wherein fluid is displaced past the pump plunger on the downstroke and is lifted on the upstroke of the pump plunger, the volume of fluid which is pumped is dependent upon the length of the stroke and the number of strokes per minute. Both of these factors are restricted by mechanical limitations; the usual pumping jacks at the surface cannot increase the pump stroke beyond the structural limits of the unit and the number of strokes per minute cannot exceed a certain amount without unduly wearing and damaging the rods, pumps and associated equipment. Attempts havebeen made to provide so-called doubleacting pumps wherein a lifting of fluid is accomplished upon the downstroke, as well as upon the upstroke of the pump plunger, but this has proven ineflicient and impractical because the weight of the pump rods is not sufficient to lift the load on the downstroke without causing bending and kinking of the rods and a resultant undue wear thereof.

It is, therefore, one object of this invention to provide an improved pump which will actually increase the fluid lifting capacity of the device without the necessity of aplying a downward force to the pump rods on the downstroke and without increasing the pump stroke or its speed of operation.

An important object is to provide an improved well pump having a double piston plunger operating within a dual cylinder arrangement, with said piston functioning to lift the fluid only upon the upstroke of the pump whereby the downstroke of the pump is merely a return stroke during which time displacement or transfer of fluid, with no lifting of the fluid column, is effected to thereby obviate excessive wear on the rods.

A further object is to provide a well pump wherein the double piston plunger and dual cylinder construction permits an increased volume of fluid to be displaced upon each upstroke of the pum mechanism.

Still another object is to provide a pump, of the character described, wherein the fluid pressures acting upon the various areas of the plunger pis- 13 Claims. (Cl. 103-181) tons and packing surfaces of the cylinder are equalized during the downstroke of the pump.

Another object is to provide a well pump wherein the plunger includes two piston elements connected by a tubular rod, with said elements operating in co-axial cylinders which are separated by a packing gland through which the tubular plunger rod reciprocates; the construction making it possible to lift an increased volume of fluid upon each upstroke of the pump.

A particular object is to provide a well pump, of the character described, which lends itself to a construction where the plunger is attached to the pump rods and is reciprocable within the barrel or where the plunger is stationary and the barrel is connected to the rods so as to be movable relative to the plunger to perform the pumping operation.

A still further object is to provide a well pump, of the character described, having an improved anchoring mean for anchoring the plunger or the barrel of the unit within the well tubing or conductor; said anchoring means being moved into connected position by longitudinal movement of the element to which it is attached and being released by a rotation of said element.

The construction designed to carry out the invention will be hereinafter described together with other features thereof.

The invention wil be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown, and wherein:

Figure 1 i a longitudinal sectional view of a well pump, constructed in accordance with the invention,

Figure 2 is an enlarged, sectional view of the lower portion of the pump,

Figure 3 is a horizontal, cross-sectional view, taken on the line 3--3 of Figure 2,

Figure 4 is a horizontal, cross-sectional view, taken on the line 44 of Figure 1.

Figure 5 is a horizontal, cross-sectional view, taken on the line 5-5 of Figure 1,

Figure 6 is a view, partly in section and partly in elevation of the coupling members of the anchoring assembly,

Figure 7 is a view, similar to Figure 1 of a modified form of the invention,

Figure 8 is an enlarged, transverse sectional view of the upper portion of the pump shown in Figure 7,

Figure 9 is a continuation of Figure 8 showing the lower portion of the pump of Figure 7,

3 Figures to 12 are horizontal, cross-sectional views, taken on the lines |ii-|, |||l and I2|2 of Figures 8 and 9, respectively.

Figure 13 is a diagrammatic View of the first form of the invention illustrated in Figures 1 to 6, and

Figure 14 is a diagrammatic view of the modified form of the invention illustrated in Figures 7 to 12.

In the drawings the numeral it designates an elongate cylindrical barrel having a bore H extending throughout its entire length. A traveling valve l2 which is downwardly closing is mounted in the upper end of the barrel Iii and permits upward flow therethrough while preventing downward flow into the barrel. The barrel is connected with the usual pump rods [3 which extend to the surface of the well bore and which are utilized to impart reciprocation to the barrel to eflect the pumping operation, as will be hereinafter explained. Intermediate the ends of the barrel is a packing assembly M, which assembly includes a plurality of upper cups or packing rings 15 and a plurality of lower cups or packing elements l8. The packing assembly functions to divide the barrel into an upper cylinder lite and a lower cylinder lob.

Extending axially within the barrel It is a tubular pump plunger ll, and the lower end of the plunger is connected with a downwardly closing standing valve I8. The standing valve is provided with an anchor collar is suitably secured thereto, and this collar is arranged to coact with an anchoring sleeve which is connected in a well conductor or tubing T. With this arrangement, the plunger I? is anchored against axial displacement with respect to the well conductor or tubing T.

The tubular pump plunger ll is formed with an upper piston 2| which is located within the upper cylinder Hia of the barrel. The area be tween this upper piston 2| and the upper packing cups l5 of the packing assembly I4 forms a chamber A within the lower portion of the cylinder lila. A lower piston 22 is mounted upon the will be effected. The upper end of the bore Ha of'the plunger Il may be closed by a downwardly closing check valve 23, but this valve is not essential and may be omitted.

Fluid from the well may enter the well conductor or tubing T below the anchoring assembly and. may pass upwardly past the standing valve l8 .and then flow into the bore Ila of the plunger IT. From the bore of the plunger fluid may enter the chamber B through radial ports or openings 24 which are formed in the pump plunger just above the lower piston 22. Upon the downstroke of the barrel l9 it will be evident that the packing assembly M moves downwardly toward the lower piston and upon this downstroke fluid within the chamber B is expelled or displaced through the ports 24; and upwardly through the tubular plunger past the check valve 23 into a chamber C provided in the extreme upper end of the barrel just below the traveling valve l2. During operation the chamber C, as

4- well as the bore of the plunger will be filled with fluid so that upon a downstroke of the barrel which displaces fluid from the chamber B, fluid is moved upwardly past the traveling valve |2 into the area D of the well conductor or tubing above the barrel.

As the barrel It moves downwardly through its downstroke the packing assembly l4 moves away from the upper piston 25 to, in eflect, enlarge the chamber A and thereby draw fluid into the chamber A through radial ports 25 provided in the wall of the barrel immediately above the packing assembly. It will, therefore, be apparent that as the barrel It] moves through its downstroke, a displacement of liquid from the chamber B upwardly through the plunger and into the area D above the barrel occurs and at the same time a filling of the chamber A takes place since the chamber A is in communication with the area exteriorly of the barrel.

Upon the upstroke of the traveling barrel Ill, the packing assembly i l of the barrel moves upwardly toward the upper piston 2| to reduce the size of the chamber A and thereby displace liquid from this chamber into the area exteriorly of the barrel and then into the area D above said barrel, whereby fluid is lifted upwardly through the well tubing or conductor T. At the same time, the upward movement of the barrel causes the packing assembly Hi to move away from the stationary lower piston 22 to, in effect, enlarge the chamber B and this results in drawing fluid upwardly past the standing valve |8, through the lower portion of the tubular plunger ii, and into the chamber B, whereby said chamher is filled during the upstroke of the barrel. Since the traveling valve i2 is closed on the upstroke of the barrel, well fluid is also drawn into the upper chamber C to fill this chamber.

Any suitable anchoring means may be employed for anchoring the plunger H in position within the well conductor or tubing '1, but it is preferable to employ the anchoring collar l9 and sleeve 28 which are clearly shown in Figures 2 and 6. The sleeve 26 is suitably threaded at each end for connection into the well conductor string and is formed nearer its lower end and within its bore with threads 26 which are of the buttress type, the cross-sectional shape of each thread being clearly shown in Figure 6. As illustrated, the lower surface of each thread actually provides an annular helical shoulder 2'1. The upper portion 20a of the bore of the sleeve 20 is of a smooth constant diameter.

The anchoring collar l9 which is threaded at its upper end for connection with the standing valve I8 is formed with external threads 28 which are complementary to the threads 26 of the sleeve with the upper surface of the threads forming a helical shoulder 2M. A plurality of longitudinal slots 29, which are illustrated as four in number, are provided in the coupling collar I9 and these slots extend from the lower end of the collar t a point. adjacent the upper part of the threaded section 28. The provision of the slots 29 imparts radial resiliency to the lower threaded portion of the collar |Q and with this arrangement it is possible to move the collar downwardly Within the sleeve 2| and by an axial force cause the threads 28 to become engaged with the threads 2%, with the surfaces 21 and 21a. abutting each other (Figure 2). The connection may thus be made between the parts without the necessity of rotating one with respect to the other. A suitable packing element 30 surrounds the upper portion of the collar H 9 and when the threads of the collar engage the threads of the sleeve this packing element contacts the bore 20a of the sleeve to seal off between the parts. The threads 26 and. 28 are preferably left hand threads so that disengagement of the collar from the sleeve may be effected by a right hand rotation of the plunger I! to which the collar I9 is attached. The particular anchoring means shown has been found especially adaptable for use in anchoring the plunger since the connection may be made by merely applying a longitudinal force to the parts and without the necessity of rotating the same. However, as above pointed out, any suitable anchor may be substituted for the specific means illustrated and described.

In the operation of the pump, reference is made to Figure 13, which is a diagrammatic view of the essential parts of the unit. Assuming the barrel [0 is to be at the upper end of its stroke, the lower chamber B, as well as the chamber C, has been filled and the fluid from the upper chamber A has been lifted. As the pump barrel l0 moves downwardly through its downstroke, the packing gland I 4 moves toward the lower piston 22 and functions to displace fluid from the chamber B through the ports 24 and into the bore of the pump plunger Ila. From this point the fluid is displaced upwardly through the check valve 23 into chamber C and fluid from the chamber C is displaced upwardly past the traveling valve l2 into the area D above and exteriorly of the barrel l0.

The downward movement of the barrel also causes the packing assembly I4 to move downwardly away from the upper piston 2| to effect an enlargement of the chamber A and to thereby fill the chamber through the ports 25. It is noted that this filling is from the area exteriorly 0f the barrel, and it might be said that upon the downstroke of the barrel the fluid from chamber B is transferred through chamber C and then into chamber A; actually, the same fluid is not transferred but the identical volume of fluid which is displaced from chamber B enters chamber A during downstroke of the barrel. It is noted that during the downstroke the pressure against the standing valve [8 will maintain this Valve in a closed position, with the check valve 23 and the traveling valve I2 being opened.

Upon a reversal of the motion of barrel l0, said barrel is moved upwardly and upon this upstroke the packing assembly l4 moves toward the upper piston 2| and functions to displace fluid from the chamber A through the ports 25 and into the area exteriorly of the barrel and also into the area above said barrel, whereby the fluid is lifted upwardly through the tubing or well conductor T. At the same time, the packing assembly is moving away from the lower piston 22 and is, in effect, enlarging the chamber B. The traveling valve 12 is maintained closed by the pressure applied through the lifting action which is lifting the fluid in the conductor and thus as the packing assembly I 4 moves away from the lower piston to enlarge the chamber B, a suction is created within the chamber B which draws fluid from the well conductor below the standing valve, upwardly past said standing valve and into said chamber B. It is thus apparent that upon the upstroke of the pump, a lifting of the fluid within the conductor or tubing T is effected and a filling of chamber B is also produced. During the upstroke, the chamber C is also filled by the suction created in this chamber during upward movement which is sufficient to unseat the check valve 23.

From the foregoing it will be seen that upon the downstroke of the barrel, fluid is transferred from chamber C to the area exteriorly of the barrel and into the chamber A; at the same time, fluid is transferred from the chamber B to the chamber 0 and this fluid is also transferred into the area exteriorly of the barrel. Upon the upstroke of the barrel fluid is displaced from chamber A and is lifted upwardly through the tubing, while chambers B and C are refilled for the next operation. With this arrangement a larger volume of fluid is handled by the pump with a given stroke and with a given number of strokes per minute. The provision of the additional chamber, together with a transfer of fluid from one chamber to another during the downstroke of the pump, makes it possible to handle the larger volume of fluid. It is noted that during the downstroke which is at the time that the chamber A is filling and displacement is occurring from chambers B and C, pressures around the packing assembly l4 and the pistons 2| and 22 are all equalized, which means that the weight of the rods is sufficient to complete the downstroke. The rods need overcome only the friction of the packing elements on the pistons and assembly [4 in order to move downwardly and therefore it is not necessary to apply downward force to the rods. This means that the rods may hang freely in tension during the downstroke and the danger of kinking or otherwise damaging said rods is eliminated.

In Figures 1 to 6 and 13, the pump has been illustrated as having the plunger ll anchored within the Well tubing or conductor, while the barrel in is movable by means of the pump rods [3. In Figures 7 to 12 and 14, a modified form of the invention is shown, wherein the plunger of the pump is attached to the pump rods while the barrel is anchored within the well conductor or tubing.

Referring to Figures 7 to 9, the modified form of pump includes a tubular pump plunger Ila; having the traveling valve [2a at its upper end and connected With the pump rods [3. The plunger Ila has an upper piston 2 la and a lower piston 2211. Above the lower piston 22a is a check valve 23a which closes the lower end of the bore and the cage of this valve has lateral openings or ports 3! which establish communication between the bore of the tubular plunger Ila above the check valve 23a and the area exteriorly of said plunger.

The pump plunger and its pistons are movable within a working barrel I H), which barrel is provided with a standing valve Hint at its lower end. The anchor collar l9 and anchor sleeve 20 are utilized to lock the barrel within the well conductor or tubing T and to seal off therebetween, as has been explained. Immediately above the standing valve Illa, the barrel I H? is formed with lateral ports or openings 32 which establish communication between the area outside of the barrel and the interior of the barrel. Since the lower end of the tubular plunger is open, it will be evident that the ports 32 establish a communication between the annular space 33 between the barrel and the well tubing and the bore of the plunger Ha.

The barrel H0 is provided with a packing assembly I [4 intermediate its ends, and said assembly divides the barrel into an upper cylinder section HM and a lower cylinder section Hill). The upper piston 2m reciprocates within the upper cylinder HM and the space between this piston and the packing assembly ll l provides an upper chamber A. This chamber is in communication with the bore of the barrel through ports a. The area between the lower piston 22a and the packing assembly He provides a lower chamber B which is in communication with the bore of the plunger Ila through the openings 3! above the check valve 23a. When the barrel HE] is in position anchored within the well conductor or tubing T, the upper end of the barrel is sealed off from the tubing or well conductor by means of a suitable sealing means 34; this sealing means may be either a metal to metal contact or suitable packing cups.

In Figure la, the modified form of well pump is illustrated schematically, and the operation of this unit may be more readily understood by L.

referring to this figure. Upon the downstroke of the plunger Ha, the upper piston 2m moves downwardly toward the packing assembly to displace fluid from the chain e A into the annulus 32a outside of the barrel H0. This displaced fluid then enters through the ports 32 and passes into the lower end of the tubular plunger Ila, unseating the check valve 33 and passing through ports 3! to fill the chamber B. At the same time, fluid moves upwardly through the tubular plunger l'la, unseating the traveling valve in and moving into the area C in the upper portion of the working barrel, which area is in communication with the bore of the well tubing or conductor T above the pump. Thus, upon the downstroke, fluid may be said to be transferred from the chamber A to the chamber B, and fluid from below the plunger 2311 has been transferred to the chamber C.

Upon the upstroke of the plunger lie, the lower piston 22a functions to lift the fluid from the chamber B through the plunger Fla and into the conductor T above the upper piston 2 la. During such upward movement fluid is lifted upwardly in the well conductor or tubing in the usual manner. At the same time, the upper piston Zia is moving upward with respect to the packing assembly lid and creates a suction beneath the upper piston Zia which will draw fluid into the chamber A. The upward movement of the lower piston 22a will create a suction therebelow which will unseat the standing valve and will fill the lower end of the working barrel. Thus, during the upward stroke of the plunger Ha, a lifting action of fluid within the conductor or tubing above the pump is effected and at the same time a filling of the chambers A and the area below the piston 22a in the lower end of the working barrel is accomplished.

Upon the next downward movement of the plunger, the fluid in the lower end of the working barrel passes upwardly through the plunger Ha into the area C thereabove and simultaneously, fluid from the chamber A is displaced downwardly into the lower end of the working barrel and then upwardly into the chamber B, whereby the next successive lifting of the plunger will lift fluid upwardly in the conductor or tubing T. It is noted that just as in the first form, during the downstroke of the plunger, pressures in and around the pistons and packing assembly H4 are equalized so that the weight of the rods are sufficient to accomplish the downstroke. There is no lifting of fluid during the downstroke but merely a transfer or displacement of fluids from one area to another, whereby no outside force need be applied to the rods. The provision of the additional chamber into which liquid is drawn during the upstroke and is transferred during the downstroke provides a pump which will handle an increased volume of fluid without any increase in the stroke length or in the number of strokes per minute of the pump. As has been noted, the particular anchoring assembly has been found especially adapted for use with a pump since the plunger or the barrel, as the case may be, may be quickly and easily anchored in position within the tubing or conductor by merely moving the parts longitudinally with respect to each other. No rotation of parts is necessary to couple the collar [9 to the sleeve 20. When the anchored part is to be removed, this may be readily accomplished by merely rotating the collar with respect to the sleeve, preferably in a right hand direction so as to eliminate possibility of uncoupling any of the rods in the string. The particular packing assembly H4, as well as the particular construction of the pistons employed in the plunger, as well as the packing elements thereof, are, of course, subject to variation and any suitable type of packing members may be employed.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

Having described the invention, I claim:

1. A well pump assembly including, a tubular barrel, an annular packing means intermediate the ends of the barrel and dividing the interior thereof into an upper cylinder and a lower cylinder, said upper cylinder having a well fluid-receiving chamber and said lower cylinder having a well fluid-receiving chamber, a tubular plunger extending axially within the barrel and slidable through the annular packing means, an upper annular piston attached to the plunger and disposed within the upper cylinder, a lower annular piston attached to the plunger and disposed within the lower cylinder, operating means extending from the surface of the well and connected with the pump assembly for imparting relative reciprocating movement between the barrel and plunger thereby effecting a relative reciprocatory movement between the pistons and their respective cylinders to alternately fill and displace fluid from the well fluid-receiving chambers, means establishing communication between the well fluid-receiving chambers and the area above the barrel, travelling valve means in said communication establishing means for controlling the flow from the well fluid-receiving chambers to the area above said barrel, a common well fluid inlet, means establishing communication between. said common inlet and both well fluid-receiving chambers, a downwardly closing standing valve controlling fiow through the common inlet, and means effective when the travelling valve'means is open during the downstroke of the pump to establish communication between the areas above and below both pistons to equalize the pressures acting upon said pistons during the downstroke.

2. A well pump assembly as set forth in claim 1, wherein the means for establishing communication between the lower well fluid-receiving chamber and the area above the barrel is the bore of the tubular plunger and a lateral opening in the plunger which is open to the lower well fluid-receiving chamber in all positions of the lower piston relative to the barrel.

3. A well pump assembly as set forth in claim 1, together with means for anchoring the lower end of the tubular plunger within a well pipe, and means for attaching the operating means to the barrel to reciprocate said barrel relative to the plunger and pistons attached thereto.

4. A well pump assembly as set forth in claim 1, together with releasable means for anchoring the lower end of the tubular plunger within a well pipe, and a connection between the operating means and the barrel, whereby the pump may be lowered into the well on the operating means and thereafter the barrel may be reciprocated relative to the plunger.

5. A well pump assembly as set forth in claim 1, together with means for anchoring the lower end of the barrel Within a well pipe, and means for attaching the operating means to the plunger to reciprocate the plunger and pistons with respect to the barrel.

6. A well pump assembly including, a tubular barrel having a fluid outlet in its upper end and a downwardly closing travelling valve controlling flow through said outlet into the area exteriorly of the barrel, an annular packing means intermediate the ends of the barrel and dividing the interior thereof into an upper cylinder and a lower cylinder, a tubular plunger extending axially within the barrel and through said annular packing means, means for anchoring the plunger within a well conductor, operating means extending from the surface secured to the barrel for reciprocating the barrel with respect to the plunger, an upper annular piston attached to the plunger and disposed within the upper cylinder, the space between the lower surface of the piston and the packing means forming an intermediate fluid-receiving chamber and the space between the upper surface of the upper piston and the travelling valve forming an upper well fluid-receiving chamber, a lower annular piston attached to the plunger and disposed within the lower cylinder, the space between the upper surface of said lower piston and the packing means forming a lower well fluid-receiving chamber, means establishing communication between the upper and lower well fluid-receiving chambers, a common well fluid inlet communicating with both well fluid-receiving chambers, a downwardly closing standing valve controlling flow through said inlet, means establishing communication between the intermediate chamber and the area below the lower surface of the lower piston, and means effective when the travelling valve is open during the downstroke of the barrel to establish communication between the intermediate chamber and the well fluid-receiving chambers whereby pressures above and below both pistons are equalized during such downstroke.

7. A well pump assembly as set forth in claim 6, wherein the means for establishing communication between the lower well fluid-receiving chamber and the upper well fluid-receiving chamber comprises the bore of the tubular plunger and a lateral port which is formed in said plunger and which is positioned to be disposed between the lower piston and the packing means in all positions of the barrel with respect to the lower piston.

8. A well pump assembly as set forth in claim 6, wherein the means for establishing communle cation between the lower well fluid-receiving chamber and the upper well fluid-receiving chamber comprises the bore of the tubular plunger and a lateral port which is formed in said plunger and which is positioned to be disposed between the lower piston and the packing means in all positions of the barrel with respect to the lower piston, and also wherein the communication between the intermediate chamber and the area exteriorly of the barrel is a lateral port in the wall of the barrel which is positioned to be located between the packing means and the upper piston in all positions of the barrel with respect to said piston.

9. A well pump assembly including, a tubular barrel having a fiuid outlet in its upper end and a downwardly closing travelling valve controlling flow through said outlet into the area exteriorly of the barrel, an annular packing means intermediate the ends of the barrel and dividing the interior thereof into an upper cylinder and a lower cylinder, a tubular plunger extending axially within the barrel and through the annular packing means, means for anchoring said plunger within a well, an upper annular piston attached to the plunger and disposed within the upper cylinder, the space between the lower surface of said upper piston and the packing means forming an intermediate fluid-receiving chamber, and the space between the upper surface of the piston and the fluid outlet in the upper end of the barrel forming an upper well fluidreceiving chamber, said intermediate chamber having communication with the area exteriorly of the barrel, a lower annular piston attached to the plunger and disposed within the lower cylinder, the space between the upper surface of said lower piston and the packing means forming a lower well fluid-receiving chamber, the lower surface of the lower piston being exposed to the fluid in the area exteriorly of the barrel, operating means extending to the surface of the well and connected with the barrel for reciprocating the barrel relative to the pistons on the anchored plunger, means for establishing communication between the lower well fluid-receiving chamber and the upper well fluid-receiving chamber, a single well fluid inlet in communication with the lower well fluid-receiving chamber, and a downwardly closing standing valve controlling flow through said inlet.

10. A well pump including, a tubular barrel having an outlet in its upper end and a downwardly closing travelling valve controlling flow through said outlet, rod means extending from the surface for reciprocating the barrel, an annular packing means intermediate the ends of the barrel and dividing the same into an upper cylinder and a lower cylinder, a stationary tubular plunger extending axially within the barrel and through the packing means, an upper piston attached to the plunger and disposed in the barrel, a lower piston attached to the plunger and disposed within the lower cylinder, the upper end of the bore of said plunger communicating with the barrel above the upper piston, an opening in the wall of the plunger establishing communication between the bore of the plunger and the area above the lower piston, means for connecting the lower end of the plunger to a well fluid source whereby said lower end of the plunger forms a well fluid inlet, a downwardly closing standing valve controlling flow through said inlet, the area between the lower end of the upper piston and the packing means forming an intermediate fluid-receiving chamber, and means establishing constant communication between the intermediate chamber and the area exteriorly of the barrel, and additional means establishing communication between the area below the lower piston and the area exteriorly of the barrel.

1-1. A well pump assembly including, a tubular barrel, means for anchoring the lower end of the barrel within the well, an annular packing means intermediate the ends of the barrel and dividing the interior thereof into an upper cylinder and a lower cylinder, a tubular plunger member extending axially Within the barrel and through the packing means, an upper piston on the plunger within the upper cylinder, the space between the lower surface of the upper piston and the packing means forming an upper fluidreceiving chamber, said chamber having an inlet opening which communicates with the area exteriorly of the barrel, a lower piston on the plunger with-in the lower cylinder, the space between the upper surface of the lower piston and the packing means forming a lower fluid receiving chamber, the plunger having a lateral opening in communication with the lower fluid receiving chamber and forming a fluid inlet for said chamber, means establishing communication between the lower end of the plunger and the area exteriorly of the barrel, a single foot valve structure at the lower end of the tubular barrel and having communication with the fluid inlets of the upper and lower fluid-receiving chambers, said foot valve structure including a downwardly closing standing valve for controlling flow of well fluids to said inlets, the upper end of the plunger having an outlet communicating with the area above the plunger and barrel, a travelling valve in the plunger, and operating means extending from the well surface for imparting reciprocating movement to the plunger to reciprocate the pistons within the barrel.

12. A well pump assembly asset forth in claim 11, together with a sealing means surrounding the upper end of the barrel for sealing 01? between the barrel and the wall of the well bore.

13. A well pump assembly including, a tubular barrel, an annular packing means intermediate the ends of the barrel and dividing the interior thereof into an uppercylinder and a lower cylinder, said upper cylinder having a well fluidreceiving chamber and said lower cylinder having a Well fluid-receiving chamber, a tubular plunger extending axially within the barrel and slidable through the annular packing means, an upper annular piston attached to the plunger and disposed within the upper cylinder, a lower annular piston attached to the plunger and disposed within the lower cylinder, operating means extending from the surface of the well and connected with the pump assembly for imparting relative reciprocating movement between the barrel and plunger thereby efiecting a relative reciprocatory movement between the pistons and their respective cylinders to alternately fill and displace fluid from the well fluid-receiving chambers, means establishing communication between the well fluid-receiving chambers and the area above the barrel, travelling valve means in said communication establishing means for controlling the flow from the well fluid-receiving chambers to the area above said barrel, a common well fluid inlet, means establishing communication between said common inlet and both well fluidreceiving chambers, a downwardly closing standing valve controlling flow through the common inlet, the plunger and barrel having passages therein adapted to communicate with each other when the travelling valve means is open to estab lish communication between both the areas above and below both pistons to thereby equalize the pressures acting upon both pistons during the downstroke of the pump.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 905,046 Baines Nov. 24, 1908 994,310 Gleason June 6, 1911 1,272,737 Walker July 16, 1918 1,643,616 Zinn Sept. 27, 1927 1,648,400 Hill Nov. 8, 1927 1,665,639 Patterson Apr. 10, 1928 1,741,913 Blankenship Dec. 31, 1929 2,074,430 Reed Mar. 23, 1937 2,356,208 Bridwell Aug. 22, 1944 2,446,748 Etter Aug. 10, 1948 2,475,739 Frank July 12, 1949 

